Microglial and astroglial cells in the rat paraclaustral reservoir during postnatal development: an...

A immunohistochemical study of postnatal development of the paraclaustral reservoir of migrating cells in the rat brain was performed using anti-GFAP (for astroglia), ED1 and OX-42 (for microglia) antibodies. From birth to the 4th day of postnatal life most GFAP-positive cells in the paraclaustral reservoir are similar to transitional astroglia. From the end of the first postnatal week they have the morphology of mature astrocytes, although during the next week, their density was a slightly higher than in neighboring structures. On the 21st day, the morphology and density of astroglial cells in the ventral part of the external capsule did not differ from the surrounding regions. ED1/OX-42- positive microglial cells present in the paraclaustral reservoir during the first postnatal week represented ameboid microglia; their density was clearly higher than in the neighboring structures. During the second week they began to transform into ramified microglia and from the 21st day on, only OX-42 positive resting microglial cells were observed in the ventral part of the external capsule. We suggest that the paraclaustral reservoir is a place of accumulation of astroglia and microglia during brain development and may possibly serve as source of glial cells for neighboring structures. Alternatively, these glial populations may perform local developmental functions.